Most Social Security Disability Insurance (SSDI) beneficiaries face a mandatory two-year waiting period for Medicare eligibility. Because of concerns that lack of health coverage during the waiting period could have life-threatening consequences for some beneficiaries, selected subpopulations are exempt from the waiting period. In 2025, legislation was introduced in Congress to expand the scope of these exemptions. However, there is limited empirical evidence on the twenty-four-month mortality rate of the SSDI beneficiary population, how it compares with that of the general population, how it varies by age and primary impairment, and how it has changed over time. Using 2000-19 Social Security Administration data, we provide a descriptive analysis of mortality rates during the Medicare waiting period. In 2019, the twenty-four-month mortality rate of SSDI beneficiaries was 5.96 percent, whereas the adjusted rate in the general population was 1.25 percent. The mortality rate was highest among beneficiaries with neoplasms, at 39.3 percent. The twenty-four-month mortality rate of SSDI beneficiaries has risen since 2011, reflecting changes in the demographic and impairment characteristics of new beneficiaries. These findings demonstrate the SSDI population's vulnerability and can inform policy conversations about expanding the scope of exemptions from the Medicare waiting period.